Synthetic Krabby Patty

See that?? Without all your smoke and mirrors, no one would stomach this garbage! —Mr. Krabs in Selling Out

Synthetic Krabby Patties were Krabby Patties served at Krabby O'Monday's. They were made from a grey-like substance that comes out of a machine, then spray-painted to look like a regular Krabby Patty, then finally heated and cooked in a furnace. Synthetic Patties sickened SpongeBob and Mr. Krabs and eventually, Mr. Krabs revealed the inside of the patty to all of the Krabby O'Monday's customers. At first, the customers enjoyed the patties, but as soon as they saw what was in the patty, most of them fled the restaurant and almost barfed it out. It appeared only in Selling Out.

Trivia

People would notice the flavor of the patty changed dramatically, especially if they were regular patrons to the Krusty Krab, and since the grey substance was used for all the components of the Krabby Patty (bun, patty, toppings, etc.)

The customers should've noticed it was grey inside, since people usually look at their food just before taking a bite out of it.

The grey goop used to make one could be a reference to pink slime that was used in McDonald's food.